_disable_selftune_checkpointing Disable self-tune checkpointing FALSE
SYS@ bys3>show parameter statistics_level --此参数为typical 或者all，再加上FAST_START_MTTR_TARGET 设置为非零值就启用MTTR Advisory
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
statistics_level string TYPICAL
SYS@ bys3>show parameter mttr
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
fast_start_mttr_target integer 0
从alert日志中数据库启动时的信息可以发现：
[oracle@bys3 ~]$ cat alert_bys3.log |grep MTTR
MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set
显式的设置alter system set FAST_START_MTTR_TARGET=0会关闭自动调节，重启数据库在alter日志中可以发现：
MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set
当FAST_START_MTTR_TARGET显示设为非零
即： statistics_level参数为typical 或者all，再加上FAST_START_MTTR_TARGET 设置为非零值就启用MTTR Advisory
此时alert日志中不会有MTTR信息--因为已经正常启动MTTR Advisory
三、关于启动MTTR Advisory时v$instance_recovery;视图的使用： --未开启MTTR Advisory时此视图内容为空。
SYS@ bys3>select mttr_target_for_estimate ,dirty_limit,estd_cache_writes ,estd_cache_write_factor ,estd_total_writes ,estd_total_write_factor from v$mttr_target_advice;MTTR_TARGET_FOR_ESTIMATE DIRTY_LIMIT ESTD_CACHE_WRITES ESTD_CACHE_WRITE_FACTOR ESTD_TOTAL_WRITES ESTD_TOTAL_WRITE_FACTOR
------------------------ ----------- ----------------- ----------------------- ----------------- -----------------------
18 1067 57 1 806 1
17 1000 57 1 806 1
19 1268 57 1 806 1
20 1507 57 1 806 1
SYS@ bys3>select target_mttr,estimated_mttr from v$instance_recovery;
TARGET_MTTR ESTIMATED_MTTR
----------- --------------
20 12
--mttr_target_for_estimate有一个值为的最接近设定的目标时间20，以及由系统计算出的的target_mttr时间20
--同时也给出了几组不同的mttr_target值及dirty_limit,cache_write,io 等来供选择，设定合适的mttr值